On the Hirudo Australis. 21 



Having succeeded in adopting a plan for their preservation 

 that requires no labour and but little attention, I see no rea- 

 son why they should not prove a remunerative article of ex- 

 port from these colonies. 



All that is required to ensure a safe passage to Great Bri- 

 tain for 1000 dozen is, that the clay should be of good quality, 

 obtained some few feet from the surface, so as to be free from 

 any impurity of the upper earth, moist, and packed in a half- 

 cask of the diameter of 3 feet, the clay being 8 inches high, 

 and occasionally moistening the top of the clay to prevent it 

 becoming hard. Should any die, they will always be found 

 on the surface, so that a change of clay is only necessary 

 about every six months. 



The cocoons I have the honour to exhibit to the members 

 of this Institute this evening, are the production of the Mur- 

 ray leech, obtained from my own small conservatory, as 

 before described — a proof sufficient that the plan I adopt is 

 more in accordance with their mode of life than that I have 

 previously mentioned. 



They bury themselves in the clay, some 6 inches from its 

 surface, when they deposit their ova, which, being attached to 

 a small pebble or to the sides of the reservoir, gradually in- 

 creases in size. 



Dr. Johnson says the leech fixes itself to some object, and 

 with its mouth fashions it into an oval body, called a cocoon. 



These cocoons are said to contain from 3 to 18 leeches. I 

 have not observed more than 3 or 4 enveloped in a brownish 

 jelly-like fluid, at first appearing like small, black spots, but 

 as the time approaches for their piercing the cocoon, they are 

 found lying attached on the whole length of the inner side 

 of the capsule, with the posterior sucker attached to the thin- 

 nest end of the cocoon, and in this manner they leave the 

 capsule. 



The cocoons, when perfect, vary in size from, f to 1 inch 

 in length, the smallest weighing about 8 grains, and the 

 largest 25 grains. They generally pierce the cocoon in about 

 40 days, if under a moderate temperature, but longer if kept 

 at a low temperature. 



Their weight, immediately after piercing the cocoon, is one 

 grain; their appearance of a brownish red color. If taken 

 then and kept in water, they die generally in a few days. 

 Their growth is said to be very slow, and must be so, for my 

 own observation shows them to increase at the rate of about 

 4 or 5 grains per annum. 



